Transformer



Jan. 19, 1954 D. KAYSER TRANSFORMER 2 Sheets-Sheet. 2

Filed Dec. 15, 1950 f h I I IHHI HI Inventor DANIEL KAYSER,

By A7614,

Attorneys Patented Jan. 19, 1954 TRANSFORMER Daniel Kayser, Paris, France, assignor to Societe Anonyme pour les Applications de lElectricite et des Gaz Bares-Etablissements Claude-Paz & Silva Application December 15, 1950, Serial No. 201,040

Claims priority, application France October 17, 1950 6 Claims.

This invention relates to a transformer with magnetic leakages for energizing, in parallel, two electric discharge devices having similar electrical characteristics, said transformer comprising, wound on the same magnetic core, one or more primary windings and two secondary windings, said two secondaries supplying respectively the two discharge devices, one of which is inductively stabilized and the other one capacitively stabilized, the inductive portions of these two stabilizations being provided, almost exclusively, by the leakage reactances of the transformer.

The method is known, of supplying two electric discharge devices of the same type from the same current source, one of said devices (the so-called lagging device), having an inductive stabilization, i. e. supplied through a reactance coil, the other one (the so-called leading device), having a capacitive stabilization, i. e. supplied through a condenser; in practice, this condenser is always in series with a reactance coil, having an impedance lower than its own at the frequency of the current source, when it is desired to obtain the advantages of this type of power supply (a smaller stroboscopic effect and a high power factor), advantages which are best obtained by a phase shift of 90 to 120 of the discharge currents of the two devices.

When the voltage of the current source is lower than the starting voltage of the discharge devices, the available voltage must be raised by means of a transformer (either with a separate primary or an auto-transformer). Since the currents delivered by the source in the primaries of the transformers supplying respectively the two discharge devices are out of phase, their resultant is substantially lower than their arithmetic sum. Consequently, one is led to raising the voltage energizing the two discharge devices by means of a single transformer comprising a single primary. In order to avoid the use of reactance coils for the inductive stabilization of the lagging device and for the inductive portion of the stabilization for the leading device, separate secondaries are used for each device, and magnetic shunts, with air gaps, are placed between the primary and each one of said secondaries.

It has been found that if such a transformer is symmetrical, i. e. if its two secondaries are similar, as well as the corresponding shunts, the shape of the curve showing the discharge current in the leading device as a function of time, is defective, which prevents the obtention of a good power factor, shortens the life of the dis- 2 charge device and decreases the light efiiciencyof the latter.

It is known that this curve shape can be improved by increasing the reluctance of the magnetic shunt placed between the primary winding and the secondary winding energizing the leading device, but this method is not very effective.

One object of this invention is to provide a transformer for energizing in parallel two electric discharge devices, whereof one is capacitively and the other one inductively stabilized, and for giving rise in these devices to discharge currents having a very good wave form.

Anotherobject is to provide a transformer in which the magnetizable core has a relatively small average cross-section, which results in an economy of laminations and wire.

One feature of this invention is that the area of the cross-section surface of the magnetizable core of the transformer is substantially larger, preferably at least twice larger, in the portions of the winding leg or legs thereof upon which is wound that secondary Winding which energizes the capacitatively stabilized electric discharge device and in those yoke portions of same core which-are traversed by the same magnetic flux as said portions of the winding leg or legs, than in the portions of same core which play the corresponding part for the other secondary.

If, for instance in the case of a shell-type transformer, the magnetic flux issuing from a portion of the winding leg is divided and traverses two or more yoke portionsin multiple, each of the crosssection surfaces of the yoke portions which are to be compared to the others is the sum of the cross-section surfaces of the yoke portions, excepting the shunt legs, which are traversed in multiple by the magnetic flux issuing from one and same portion of winding leg.

Other objects and features of the invention will in part be obvious, and will in part be explained hereinafter.

In drawings, which illustrate embodiments of the invention,

Figure l is a top plan view of the magnetic circuit of an embodiment of the invention,

Figure 2 is an elevation of the same magnetic circuit; the separate laminations of the iron stack up are shown at the ends only, for greater clearness of the figure,

Figure 3 is a schematic diagram showing the application of the transformer according to Figures 1 and 2 to the energization of two discharge devices,

Figure 4 is a section of the core of the magnetic circuit of another embodiment, along a plane perpendicular to the laminations of said core, the separate ,laminations being shown at the ends only.

Figure 5 is a section, similar to that of Figure 4, of still another embodiment.

The magnetic circuit of the transformer shown as an embodiment in Figures 1 and 2 comprises a core, 9, I2, l6, two yokes, 8, l8, and two outside legs I, 4, 1 and l9, l3, H. The core and legs in section along lines BB, .AA, C-C of Figure 1, have the same shapes and dimensions. As shown by the elevational view represented in Figure 2, the core and legs comprise each three portions of different thicknesses, but of the same width. The yokes, 8 and I8, have the same thickness, respectively, as the adjacent portions 9 and I6 of the core, and their length is half that of said core; the portions I and H of the legs have the same thickness as the portion of the core, portions 4 and [3 of the legs have the same thickness as the portion l2 of thecore, portions 1 and I9 of the legs have the same thickness as the portion 9 of the core, and the uniform width of said legs is half the width of the core.

This magnetic circuit also comprises four magnetic shunts, 2, 6, l0, 15, located between the core and legs and separated from the latter by air gaps 3, 34, 5, 35, H, 36, M, 31, in which are housed plates of insulating and non magnetic material in order to hold the shunts in position. The primary winding is wound on the central portion I2 of the core, the secondary supplying the leading discharge device on the portion 9 having a larger cross section, the other secondary on portion 15 having a smaller cross section. It may be indicated, by way of example, that the core offers a uniform width of 40 mm., and thickness of 20, 40, 60 mm. respectively, in its portions [6, l2, 9, and that the yokes and legs have a uniform width of mm. The distance between the legs and core, which is the thickness of the space in which the various windings are housed, is 20 mm. For the same transformer, the thickness of the magnetic shunts is 6 mm. and the air gap, for instance 3, 34 or 5, 35, between the shunts and the core and legs respectively, is 0.5 mm. on either side of each shunt. The length of the magnetic shunts, inserted in the space between the cores and legs, i. .e. the length inserted between the two parts to be shunted, varies from one transformer to another of the same type, this being the adjustment method used for compensating the inevitable variations in industrial construction; an example will be given later of the insertion lengths adopted.

The primary of the transformer represented is wound on the portion [2 of the core-and comprises 770 turns. The secondary which supplies the leading discharge device comprises, 2,470 turns and the other secondary 3,200 turns; each one of these windings gives, in open circuit, a voltage of 750 volts when the primary is energized by 220 volts.

Figure 3 shows the energization, from an alternating current source 26, 21., of 220 volts, of two discharge devices 30, 3|, with capacitive and inductive stabilizations respectively. These devices, in the present case, are fluorescent lamps 250 cm. long, and mm. in diameter, starting without any pre-heating, provided with low voltage drop electrodes; their starting voltage is about 600 volts and their discharge voltage, in operation, is 320 volts. The necessary voltage rise, is cffected by the above described transformer, of which, for simplification, the magnetic circuit is represented on Figure 3 only by its core Q, l2, I6, and two shunts l0, l5; this same transformer provides the inductive parts of the stabilizations for the two lamps. One end of each one of the two secondary coils may be connected through the lead 38 with an earth, so that only three wires instead of four are necessary for connecting the two lamps wtih the transformer. Lamp 30 is in series with a condenser 32 of 0.7 microfarad.

In one embodiment, effective inserted shunt lengths 20, 21 and 22, 23, of 40 and 20 re spectively give the same operating currents in the two lamps, namely 0.270 amps. together with a power factor of 0.95 for the whole and an excellent current curve shape. It was also found that wide variations of these lengths have only a small effect on the power factor, the curve shape and the open circuit voltage.

In open circuit operation, the average induction is of the order of 9,000 gauss in the portion of the core inside the primary; it is somewhat higher inside the secondary which supplies the lagging lamp and a little lower inside the secondary supplying the leading lamp. Under load, the corresponding average inductions are about 9,000., 6.6.00 and 10,000 gauss. It will be seen that the magnetic core is little saturated, which is the reason for the very good current curve shape obtained. This advantage results, in particular, in the electrodes of lamps '30, 31, being little stressed and having a long life, and in the luminous efficiency of these lamps being lab.

The above described embodiment comprises only one primary winding, but it is obvious that this winding may be replaced by several coils supplied in series or parallel from the current source. Iwo primaries might be provided, for instance, wound respectively one on a magnetic circuit carrying the lagging secondary and the other one on a circuit carrying the leading secondary, these circuits .having larger cross sections in the second case than in the first one; these two magnetic circuits are contiguous along one of their yokes or have a common yoke, so as to let the magnetic flux pass easily from one to the other.

The above embodiment has been described only to facilitate the understanding of the invention, and no way limitative.

Numerous other modifications might also be imagined within thescope of the invention. For example,

Figure 4 shows the magnetic core of a further transformer; the portion 4 l, upon which is wound the primary winding of the transformer, has a cross-section of the same shape and area as the portion 42 upon which is wound that secondary which energizes the leading electricdischarge lamp.

Figure 5 shows the core of still another transformer of the invention; the cross-section of the portion 44 of this core, upon which is wound the primary winding, has the same shape and the same area as those of the portion 43 upon winch is wound "that secondary which energizes the lagging electric discharge lamp.

An unshielded magnetic circuit could also be used, or the primary might be connected with the secondaries so as to constitute an auto-trans former, or again each one of the lamps 30, ii, might be replaced by several lamps, mounted in series, and said lamps might be started succes sively in each series; the transformers accordin to the invention also allow the starting of the lamps by pre-heating of their electrodes.

I claim:

1. A transformer for supplying electrically displaced currents for operating two electric discharge devices, comprising, a magnetizable core having yoke portions and at least one winding leg, on said winding leg a primary energizing winding and a first and a second secondary windthe magnetic leakages between said primary winding and said secondary windings being substantiai, each secondary winding having leads for connecting it to one of the discharge devices and a condenser being connected in series with said first secondary winding for causing it to furnish a leading current, the cross-section surface of the winding leg being substantially larger in the portion thereof upon which is wound said first secondary than in the portion upon which is wound said second secondary, and the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said first secondary winding being substantially larger than the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said second secondary winding.

2. A transformer for supplying electrically displaced currents for operating two electric discharge devices, comprising, a magnetizable core having yoke portions and at least one winding leg, on said winding leg a primary energizing winding, a first and a second secondary winding, and shunt legs between said primary winding and said secondary windings, each secondary winding having leads for connecting it to one of the discharge devices and a condenser being connected in series with said first secondary winding for causing it to furnish a leading current, the crosssection surface of the winding leg being substantially larger in the portion thereof upon which is wound said first secondary than in the portion upon which is wound said second secondary, and the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said first secondary winding being substantially larger than the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said second secondary winding.

3. A transformer for supplying electrically displaced currents for operating two electric discharge devices, comprising, a magnetizable core having yoke portions and at least one winding leg, on said winding leg a primary energizing winding and a first and a second secondary winding, the magnetic leakages between said primary winding and said secondary windings being substantial, each secondary winding having leads for connecting it to one of the discharge devices and a condenser being connected in series with said first secondary winding for causing it to furnish a leading current, the cross-section surface of the winding leg being at'least twice as large in the portion thereof upon which is wound said first secondary as in the portion upon which is wound said second secondary, and the crosssection surface or" those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said first secondary winding being at least twice as large as the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said second secondary winding.

4. A transformer for supplying electrically displaced currents for operating two electric discharge devices, comprising, a magnetizable core having yoke portions and at least one winding leg, on said winding leg a primary energizing winding and a first and a second secondary winding, the magnetic leakages between said primary winding and said secondary windings being substantial, each secondary winding having leads for connecting it to one of the discharge devices and a condenser being connected in series with said first secondary winding for causing it to furnish a leading current, the cross-section surface of the winding leg being at least twice as large in the portion thereof upon which is wound said first secondary as in the portion upon which is wound said second secondary and as in the portion upon which is wound said primary winding, the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said first secondary winding being at least twice as large as the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said second secondary winding, and at least twice as large as the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said primary winding.

5. A transformer for supplying electrically displaced currents for operating two electric discharge devices, comprising, a magnetizable core having yoke portions and at least one winding leg, on said winding leg a primary energizing winding and a first and a second secondary winding, the magnetic leakages between said primary winding and said secondary windings being substantial, each secondary winding having leads for connecting it to one of the discharge devices and a condenser being connected in series with said first secondary winding for causing it to furnish a leading current, the cross-section surface of the winding leg being substantially larger in the portions thereof upon which are wound said first secondary and said primary winding than in the portion upon which is wound said second secondary winding, and the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which are wound said first secondary and said primary winding being substantially larger than the cr0ss-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of the winding leg upon which is wound said second secondary winding.

6. A transformer for supplying electrically displaced currents for operating two electric discharge devices, comprising, a magnetizable core having yoke portions and at least one winding leg, on said winding leg a primary energizing winding and a first and a second secondary winding, the magnetic leakages between said primary winding and said secondary windings being substantial, each secondary winding having leads for connecting it to one of the discharge devices and a condenser being connected in series with said first secondary winding for causing it to furnish a leading current, the crosssection surface of the winding leg being substantiailyiarger in the portion thereof upon which is wound said firstsecondary than in theportion upon which is wound said primary winding and being substantially larger in the latter portion than in the portion upon which is wound said second secondary winding, and the cross-section surface of those yoke portions which are traversed by the same magnetic flux as the portions of thewinding iegjupon which is Wound said first secondary winding being substantially larger than the cross-section surface of those yoke portions which are traversed'by the same magnetic flux as the portions of the winding leg upon which is wound said primary winding and being substantially larger in the latter yoke portions than "the cross-section surface of those yoke portions which are traversed by the same magnetic flux as those portions of the windingleg upon which is wound said second secondary winding.

DANIEL KAYSER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,874,806 Ross Aug. 30, 1932 2,298,935 Freeman Oct. 13-, 1942 

